
#include<stdio.h>
//typedef int Int;
#define pi 4.0*atan(1.0)
int main()
{
    double radius;
    double area;

    scanf("%lf",&radius);
    if(radius<0)
        area=-1;
    else
        area=pi*radius*radius;

    if(area>=0)
        printf("%.6f\n",area);
    else
        puts("Are you kidding?");
    return 0;
}
